Battery pack heating system and control method thereof

ABSTRACT

A battery pack heating system includes: a main positive switch, a main negative switch, an inverter, an external port, a motor, a control module for auxiliary charging branch, a vehicle control unit, a motor control unit, and a battery management module. The battery management module is configured to send, when an acquired state parameter of the battery pack meets a preset low-temperature-low-power condition, a low-temperature-low-power heating request instruction to the vehicle control unit and the control module respectively. The control module is configured to send a first control signal to control the auxiliary charging branch to be connected. The vehicle control unit is configured to send a second control signal to enable the motor control unit to control on-off of the switch modules in the inverter, and a third control signal to enable the battery management module to control on-off of the main positive switch.

CROSS-REFERENCE OF RELATED APPLICATION

The application is a continuation of International Application No.PCT/CN2020/087767 filed on Apr. 29, 2020, which claims priority toChinese Patent Application No. 201910547455.8 filed on Jun. 24, 2019 andentitled “BATTERY PACK HEATING SYSTEM AND CONTROL METHOD THEREOF”. Theapplications are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present application generally relates to batteries, and moreparticularly to a battery pack heating system and a control methodthereof.

BACKGROUND

With the development of new energy, it is used as power in more and morefields. Battery is widely used in new energy vehicles, consumerelectronics, energy storage systems and other fields, due to itsadvantages, such as high energy density, recyclable charging capability,good safety, environmental friendly, and the like.

However, use of battery in a low temperature environment is subject tocertain restrictions. Specifically, discharge capacity of the battery inthe low temperature environment would degrade severely, and the batterycannot be charged in the low temperature environment. Therefore, inorder to be able to use the battery normally, it is necessary to heatthe battery in the low temperature environment.

Currently, a heat-circulating container may be dedicatedly provisionedfor the battery. Heat-conducting material in the heat-circulatingcontainer can be heated and heat can be transferred to the battery. As aresult, the battery is heated indirectly. However, such a heating methodtakes a long time and heating efficiency is low.

SUMMARY

Embodiments of the present application provide a battery pack heatingsystem and a control method thereof, which may improve heatingefficiency of a battery pack.

In a first aspect, an embodiment of the present application providesbattery pack heating system, including: a main positive switch connectedto a positive electrode of a battery pack, a main negative switchconnected to a negative electrode of the battery pack, an inverterconnected to the main positive switch and the main negative switch, anexternal port connected to the inverter, a motor connected to theinverter, a control module for auxiliary charging branch, a vehiclecontrol unit, a motor control unit, and a battery management module,wherein: the inverter includes a plurality of switch modules; theexternal port is connected to an auxiliary charging branch, and theauxiliary charging branch includes a power supply; the batterymanagement module is configured to acquire a state parameter of thebattery pack, and send, when the state parameter of the battery packmeets a preset low-temperature-low-power condition, alow-temperature-low-power heating request instruction to the vehiclecontrol unit and the control module for auxiliary charging branchrespectively; the control module for auxiliary charging branch isconfigured to send a first control signal to the auxiliary chargingbranch in response to the low-temperature-low-power heating requestinstruction to control the battery pack heating system to be connectedto the auxiliary charging branch so as to enable the power supply totransmit energy to the battery pack and/or the motor via the externalport; and the vehicle control unit is configured to send, in response tothe low-temperature-low-power heating request instruction, a secondcontrol signal to the motor control unit to enable the motor controlunit to control on-off of the switch modules in the inverter, and athird control signal to the battery management module to enable thebattery management module to control on-off of the main positive switchto enable transmission of energy between the battery pack and the motor,so as to heat the battery pack.

In a second aspect, an embodiment of the present application provides acontrol method for a battery pack heating system applicable to thebattery pack heating system in the first aspect. The control method forthe battery pack heating system includes: acquiring, by the batterymanagement module, a state parameter of the battery pack, and sending alow-temperature-low-power heating request instruction to the vehiclecontrol unit and the control module for auxiliary charging branchrespectively when the state parameter of the battery pack meets a presetlow-temperature-low-power condition; sending, by the control module forauxiliary charging branch, a first control signal to the auxiliarycharging branch in response to the low-temperature-low-power heatingrequest instruction to control the battery pack heating system to beconnected to the auxiliary charging branch, so as to enable the powersupply to transmit energy to the battery pack and/or the motor via theexternal port; and sending, by the vehicle control unit in response tothe low-temperature-low-power heating request instruction, a secondcontrol signal to the motor control unit to enable the motor controlunit to control on-off of the switch modules in the inverter, and athird control signal to the battery management module to enable thebattery management module to control on-off of the main positive switchto enable transmission of energy between the battery pack and the motor,so as to heat the battery pack.

Embodiments of the present application provide a battery pack heatingsystem and a control method thereof. The battery management module maydetermine that the state parameter of the battery pack meets the presetlow-temperature-low-power condition, and send alow-temperature-low-power heating request instruction to the vehiclecontrol unit and the control module for auxiliary charging branchrespectively for a low-temperature-low-power heating mode. The batterymanagement module may control the control module for auxiliary chargingbranch, and the vehicle control unit may control the battery managementmodule and the motor control unit, then the auxiliary charging branch,the main positive switch and the switch modules in the inverter can becontrolled to enable the power supply of the auxiliary charging branchto transmit energy to the battery pack and/or the motor, so that thebattery pack and motor can have sufficient energy to support heating ofthe battery pack. The battery pack and the motor may transmit energy toeach other to form a cycle in which the battery pack is charged anddischarged, so that a current is generated in a circuit in which thebattery pack is located. The alternating current may continuously passthrough the battery pack, so that the internal resistor of the batterypack may emit heat. As a result, uniform and highly efficientself-heating of the battery pack can be realized even in the case of lowpower.

BRIEF DESCRIPTION OF THE DRAWINGS

The present application will be better understood by reading thefollowing detailed description with reference to the appended drawings,in which the same or similar numerals represent the same or similarfeatures.

FIG. 1 is a schematic structure diagram of a battery pack heating systemaccording to an embodiment of the present application.

FIG. 2 is a schematic structure diagram of a battery pack heating systemaccording to another embodiment of the present application.

FIG. 3 is a flow chat of a control method for a battery pack heatingsystem according to an embodiment of the present application.

FIG. 4 is a flow chat of a control method for a battery pack heatingsystem according to another embodiment of the present application.

FIG. 5 is a flow chat of a control method for a battery pack heatingsystem according to yet another embodiment of the present application.

DETAILED DESCRIPTION

Features of various aspects and exemplary embodiments of the presentapplication will be described in detail below. In the following detaileddescription, many specific details are disclosed to provide a thoroughunderstanding of the present application. However, it is apparent to aperson skilled in the art that the present application may be practicedwithout some of these specific details. The following descriptions ofembodiments are merely to provide a better understanding of the presentapplication through illustrating examples of the present application.The present application is by no means limited to any specificconfiguration and algorithm disclosed below, but rather covering anymodification, substitution, and improvement of elements, components, andalgorithms without departing from the spirit of the present application.In the appended drawings and the following descriptions, well-knownstructures and techniques are not illustrated to avoid unnecessarilyobscuring the present disclosure.

Embodiments of the present application provide a battery pack heatingsystem and a control method thereof, which may be applied to a scenewhere a battery pack is heated under a condition with low temperatureand low state of charge (SOC) of the battery pack. With the battery packheating system and the control method for the battery pack heatingsystem in the embodiments of the present application, the temperature ofthe battery pack can be raised to a temperature at which the batterypack may operate normally. The battery pack may include at least onebattery module or at least one battery cell, which is not limitedherein. The battery pack can be applied to an electric vehicle to supplypower to the motor as a power source of the electric vehicle. Thebattery pack may also supply power to other electric devices in theelectric vehicle, which is not limited herein.

In an embodiment of the present application, with control of the batterypack heating system, when the state parameter of the battery pack meetsthe preset low-temperature-low-power condition, the power supply in theauxiliary charging branch may provide the battery pack and/or the motorwith a portion of energy transferred between the battery pack and themotor that is required for heating the battery pack. That is, the sum ofthe energy supplied by the power supply in the auxiliary charging branchand the original energy in the battery pack and the motor are sufficientto support the heating of the battery pack. As a result, the batterypack can be charged under a condition of low temperature and low power,and the charging efficiency can be improved.

FIG. 1 is a schematic structure diagram of a battery pack heating systemaccording to an embodiment of the present application. As shown in FIG.1 , the battery pack heating system may include a main positive switchK1 connected to a positive electrode of a battery pack P1, a mainnegative switch K2 connected to a negative electrode of the battery packP1, an inverter P2 connected to the main positive switch K1 and the mainnegative switch K2, external ports G1 and G2 connected to inverter P2, amotor P3 connected to the inverter P2, a control module for auxiliarycharging branch P8, a vehicle control unit (Vehicle Control Unit, VCU)P5, a motor control unit (Motor Control Unit, MCU) P7, and a batterymanagement module P6. The battery management module P6 may be a batterymanagement system (Battery Management System, BMS). The control modulefor auxiliary charging branch P8 may be a circuit control unit (CircuitControl Unit, CCU).

In some examples, a safety module may be disposed between the batterypack P1 and the main positive switch K1, or safety modules may bedisposed between a plurality of battery cells connected in the batterypack, which is not limited herein. In some examples, the safety modulemay be a manual service disconnect (Manual Service Disconnect, MSD).

The inverter P2 may include a plurality of switch modules.

In some examples, as shown in FIG. 1 , inverter P2 includes a firstphase bridge arm, a second phase bridge arm, and a third phase bridgearm that are connected in parallel. The first phase bridge arm, thesecond phase bridge arm, and the third phase bridge arm each have anupper bridge arm and a lower bridge arm. The upper bridge arm may beprovided with a switch module, and the lower bridge arm may be providedwith a switch module. That is, the first phase bridge arm is a U-phasebridge arm, the switch module of the upper bridge arm of the U-phasebridge arm is a first switch module, and the switch module of the lowerbridge arm of the U-phase bridge arm is a fourth switch module. Thesecond phase bridge arm is a V-phase bridge arm, the switch module ofthe upper bridge arm of the V-phase bridge arm is a second switchmodule, and the switch module of the lower bridge arm of the V-phasebridge arm is a fifth switch module. The third phase bridge arm is a Wphase bridge arm, the switch module of the upper bridge arm of the Wphase bridge arm is a third switch module, and the switch module of thelower bridge arm of the W phase bridge arm is a sixth switch module P26.

In some examples, the switch modules may include one or more of aninsulated gate bipolar transistor (Insulated Gate Bipolar Transistor,IGBT) chip, an IGBT module, a metal-oxide-semiconductor field-effecttransistor (Metal-Oxide-Semiconductor Field-Effect Transistor, MOSFET),and other power switches. Here, the combination and connection manner ofeach IGBT device, MOSFET device, and the like in the switch modules arenot limited. Material type of the above power switches is also notlimited. For example, a power switch made of silicon carbide (i.e., SiC)or other materials may be used.

Specifically, the switch module(s) has a diode(s). For the switch moduleof the upper bridge arm, the anode of the diode may be connected to theconnection point of the upper bridge arm and the lower bridge arm, andthe cathode of the diode may be located between the upper bridge arm andthe main positive switch K1. For the switch module of the lower bridgearm, the anode of the diode may be located between the lower bridge armand the main negative switch K2, and the cathode of the diode may beconnected to the connection point of the upper bridge arm and the lowerbridge arm.

In some examples, the switch module may include a power switch. Thediode of the above power switch may be a parasitic diode or a speciallydesigned diode. The material type of the diode is also not limited. Forexample, a diode made of silicon (i.e., Si), silicon carbide (i.e.,SiC), or other materials may be used.

The inverter P2 may be connected to the motor P3. In some examples, asshown in FIG. 1 , the first phase input terminal, the second phase inputterminal, and the third phase input terminal of the motor P3 arerespectively connected to the connection point of the upper bridge armand the lower bridge arm of the first phase bridge arm, the connectionpoint of the upper bridge arm and the lower bridge arm of the secondphase bridge arm, and the connection point of the upper bridge arm andthe lower bridge arm of the third phase bridge arm.

For example, as shown in FIG. 1 , the stator of motor P3 is equivalentto three-phase stator inductors and resistors. The stator inductor(s) iscapable of energy storage. The stator inductor and resistor in eachphase are connected to a phase bridge arm. The three-phase statorinductors are taken as a first stator inductor L1, a second statorinductor L2, and a third stator inductor L3, respectively. A firstresistor R1 is correspondingly connected to the first stator inductorL1, a second resistor R2 is correspondingly connected to the secondstator inductor L2, and a third resistor R3 is correspondingly connectedto the third stator inductor L3. The first phase input terminal, thesecond phase input terminal, and the third phase input terminal of themotor P3 may be used as an input terminal to input current, and may alsobe used as an output terminal to output current.

Specifically, one end of the first stator inductor L1 may be the firstphase input terminal, and the other end of the first stator inductor L1may be connected to one end of the second stator inductor L2 and one endof the third stator inductor L3. The other end of the second statorinductor L2 may be the second phase input terminal. The other end of thethird stator inductor L3 may be the third phase input terminal.

The external ports G1 and G2 may be connected to an auxiliary chargingbranch P4. The auxiliary charging branch P4 may include a power supplyP41. For example, the external ports G1 and G2 may be high voltagecharging interfaces. In some examples, the power supply P41 may be avoltage source for which voltage is adjustable.

The battery management module P6 may be configured to obtain a stateparameter of the battery pack P1. If the state parameter of the batterypack P1 meets a preset low-temperature-low-power condition, the batterymanagement module P6 may be configured to send alow-temperature-low-power heating request instruction to the vehiclecontrol unit P5 and the control module for auxiliary charging branch P8respectively. If the state parameter of the battery pack P1 meets thepreset low-temperature-low-power condition, it is indicated that thestate parameter of the battery pack P1 is insufficient to support normaloperation of the battery pack P1. The low-temperature-low-power heatingrequest instruction may be used to instruct the battery pack heatingsystem to enter a low-temperature-low-power heating mode.

In some examples, the state parameter may include a temperature and astate of charge (SOC). The preset low-temperature-low-power conditionmay include the temperature being lower than a heating temperaturethreshold, and the SOC is lower than a heating SOC requirementthreshold. If the state parameter meets the presetlow-temperature-low-power condition, it is indicated that thetemperature of the battery pack P1 is insufficient to support the normaloperation of the battery pack P1 and the SOC of the battery pack P1 isinsufficient to support the heating of the battery pack P1.

The temperature of the battery pack P1 herein may be the temperature ofthe house of the battery pack P1 or the temperature of the air withinthe internal space of the battery pack P1, or the temperature of any oneof battery packs P1 or battery cells, or an average value oftemperatures of all the battery cells in the battery pack P1, etc.,which is not limited herein.

The heating temperature threshold may be the minimum temperature atwhich the battery pack P1 can operate normally, that is, the temperaturethreshold at which the battery pack heating system needs to be heated.The heating temperature threshold may be set based on operating scenesand operating requirements, which is not limited herein. For example,the heating temperature threshold may be any of the threshold range[−50° C., 5° C.]. If the temperature of the battery pack P1 is lowerthan the heating temperature threshold, the battery pack P1 cannotoperate normally and needs to be heated.

The heating SOC requirement threshold may be a SOC required to performthe current heating of the battery pack P1, that is, a SOC thresholdrequired for the battery pack heating system to heat the battery packP1. The heating SOC requirement threshold may be preset based onoperating scenarios and the operating requirements, or may be estimatedby the battery management module P6 according to the current temperatureof the battery pack P1, which is not limited herein. For example, theheating SOC requirement threshold may be any one of the threshold range[5%, 100%). If the temperature of the battery pack P1 is lower than theheating temperature threshold, and the SOC of the battery pack P1 islower than the heating SOC requirement threshold, the power supply P41of the auxiliary charging branch P4 is required to provide at least partof energy required for heating the battery pack P1.

The control module for auxiliary charging branch P8 may be configured tosend a first control signal to the auxiliary charging branch P4 inresponse to the low-temperature-low-power heating request instruction tocontrol the battery pack heating system to be connected to the auxiliarycharging branch P4, so as to enable the power supply P41 to transmitenergy to the battery pack P1 and/or the motor P3 via the external portsG1 and G2.

The vehicle control unit P5 may be used to send a second control signalto the motor control unit P7 to enable the motor control unit P7 tocontrol on-off of the switch modules in the inverter P2.

The vehicle control unit P5 may be further configured to send a thirdcontrol signal to the battery management module P6 to enable the batterymanagement module P6 to control on-off of the main positive switch K1.

On one hand, the second control signal and the third control signal sentby the vehicle control unit P5 may cooperate with the first controlsignal sent by the control module for auxiliary charging branch P8 toenable the power supply P41 of the auxiliary charging branch P4 transmitenergy to the battery pack P1 and/or the motor P3 via the external portsG1 and G2. That is, the battery pack P1 may receive the energytransmitted from the power supply P41 of the auxiliary charging branchP4, and/or the motor P3 may receive the energy transmitted from thepower supply P41 of the auxiliary charging branch P4. On the other hand,the second control signal and the third control signal may cooperate toenable transmission of energy between the battery pack P1 and the motorP3 so as to heat the battery pack P1. That is, the energy may betransmitted from the battery pack P1 to the motor P3, and thentransmitted back to the battery pack P1 from the motor P3, and so on.Such a circulation forms a plurality of cycles of charging anddischarging of the battery pack P1. As a result, an alternating currentmay be generated in the circuit in which the battery pack P1 is located.

In some examples, the vehicle control unit P5 may also control, inresponse to the low-temperature-low-power heating request instruction,an onboard instrument to issue a prompt message to prompt the user aboutselection of whether to allow the low-temperature-low-power heatingrequest instruction. If an input indicating allowance of thelow-temperature-low-power heating request instruction is received, thecontrol module for auxiliary charging branch P8 may subsequentlytransmit the first control signal, and the vehicle control unit P5 maytransmit the second control signal and the third control signals, etc.

It should be noted that, before the battery management module P6 obtainsthe state parameter of the battery pack P1 and determines that the stateparameter of the battery pack P1 meets the presetlow-temperature-low-power condition, power-on self-inspection of thevehicle may be performed first. If the power-on self-inspection of thevehicle is normal, the battery management module P6 may compare thestate parameter of the battery pack P1 and the preset low-temperaturelow-power condition. Specifically, when the user turns on the Key_On ofthe vehicle via a key, and the vehicle control unit P5 may receive atrigger power-on signal to trigger the power-on. Self-inspection of thevehicle control unit P5 may be performed to inspect whether or not thevehicle is normal, and if not, a vehicle fault information may bereported. The battery management module P6 may also perform inspectionto inspect whether there is a failure in the battery management moduleP6 and the battery pack P1, and if a failure occurs, it may send abattery management failure information to the vehicle control unit P5.Then the comparison of the state parameter of the battery pack P1 andthe preset low-temperature-low-power condition is not performed by thebattery management module P6. The vehicle control unit P5 may report thebattery management fault information once it is received. Similarly, themotor control unit P7 may also perform inspection. If the motor controlunit P7 detects that the vehicle is running at the moment, it may send anotification message to the vehicle control unit P5. The vehicle controlunit P5 may control the battery management module P6 not to perform thecomparison of the state parameter of the battery pack P1 and the presetlow-temperature-low-power condition. That is, when the batterymanagement module P6, the battery pack P1, the vehicle control unit P5,the motor control unit P7, and the motor P3 are all in a normal state,the battery management module P6 may perform the comparison of the stateparameter of the battery pack P1 and the presetlow-temperature-low-power conditions and subsequent operations.

In an embodiment of the present application, the battery managementmodule P6 may determine that the state parameter of the battery pack P1meets the preset low-temperature-low-power condition, and send thelow-temperature-low-power heating request instruction to the vehiclecontrol unit P5 and the control module for auxiliary charging branch P8,respectively to request to operate in a low-temperature-low-powerheating mode. The battery management module P6 may control the controlmodule for auxiliary charging branch P8, and the vehicle control unitmay control the battery management module P6 and the motor control unitP7, then the auxiliary charging branch P4, the main positive switch K1and the switch modules in the inverter P2 can be controlled to enablethe power supply P41 of the auxiliary charging branch P4 to transmitenergy to the battery pack and/or the motor P3, so that the battery packP1 and motor P3 can have sufficient energy to support heating of thebattery pack P1. The battery pack P1 and the motor P3 may transmitenergy to each other to form a cycle in which the battery pack P1 ischarged and discharged, so that a current is generated in a circuit inwhich the battery pack P1 is located. The alternating current maycontinuously pass through the battery pack P1, so that the internalresistor of the battery pack P1 may emit heat. As a result, uniform andhighly efficient self-heating of the battery pack can be realized evenin the case of low power.

FIG. 2 is a schematic structure diagram of a battery pack heating systemaccording to another embodiment of the present application. As shown inFIG. 2 , the battery pack heating system further includes a supportcapacitor C1, a pre-charging branch P9, and the auxiliary chargingbranch P4. The auxiliary charging branch P4 described above may furtherinclude an auxiliary switch module.

For convenience of description, in an embodiment of the presentapplication, each device shown in FIG. 2 will be taken as an example fordescription. The first switch module includes a first power switch S1,the second switch module includes a second power switch S2, the thirdswitch module includes a third power switch S3, the fourth switch moduleincludes a fourth power switch S4, the fifth switch module includes afifth power switch S5, and the sixth switch module includes a sixthpower switch S6. The diode of the first power switch S1 is VD1, thediode of the second power switch S2 is VD2, the diode of the third powerswitch S3 is VD3, the diode of the fourth power switch S4 is VD4, thediode of the fifth power switch S5 is VD5, and the diode of sixth powerswitch S6 is VD6.

The control module for auxiliary charging branch P8 may be configured tosend the first control signal to the auxiliary switch module in responseto the low-temperature-low-power heating request instruction to controlthe auxiliary switch module to be turned on. That is, the auxiliaryswitch module may be turned on in response to the first control signal.The auxiliary switch module in the auxiliary charging branch P4 may be aswitch K3. Then the switch K3 may be turned on in response to the firstcontrol signal.

The pre-charging branch P9 may be connected in parallel with the mainpositive switch K1. The pre-charging branch P9 may include apre-charging switch K4 and a pre-charging resistor.

The battery management module P6 may be further configured to send athird driving signal to the pre-charging switch K4 to control thepre-charging switch K4 to be turned on for pre-charging. It should benoted that the pre-charging switch K4 is turned on, the main positiveswitch K1 is turned off, the main negative switch K2 is turned on, thenthe battery pack P1, the pre-charging branch P9, the support capacitorC1, and the main negative switch K2 form a loop for pre-charging.

When the battery management module P6 detects that the pre-charging iscompleted, the third driving signal is stopped from being sent to thepre-charging switch K4 to control the pre-charging switch K4 to beturned off, and the pre-charging is finished.

Function and specific operation of each part of the battery pack heatingsystem in the low-temperature-low-power heating mode will be describedbelow.

Specifically, the motor control unit P7 may be configured to send afirst driving signal to a portion of the switch modules in the inverterP2 in response to the second control signal, to drive the portion of theswitch modules to be periodically turned on and off, so as to enable themotor P3 to receive the energy transmitted from the power supply P41, orenable the motor P3 to receive energy transmitted from the battery packP1, or enable the motor P3 to transmit energy to the battery pack P1.

The switch modules that are turned on in response to the first drivingsignal include a target upper bridge arm switch module and a targetlower bridge arm switch module. The target upper bridge arm switchmodule is the switch module of the upper bridge arm of any bridge arm ofthe first phase bridge arm, the second phase bridge arm, and the thirdphase bridge arm. The target lower bridge arm switch module is theswitch module of the lower bridge arm of at least one of the first phasebridge arm, the second phase bridge arm, and the third phase bridge armother than the bridge arm that includes the target upper bridge armswitch module.

It should be noted that the switch modules that are not driven by thefirst driving signal are all turned off. That is, the switch modulesexcept the target upper bridge arm switch module and the target lowerbridge arm switch module are turned off.

For example, as shown in FIG. 2 , if the target upper bridge arm switchmodule is the first switch module, the target lower bridge arm switchmodule is the fifth switch module and/or the sixth switch module. If thetarget upper bridge arm switch module is the second switch module, thetarget lower bridge arm switch module is the fourth switch module and/orthe sixth switch module. If the target upper bridge arm switch module isthe third switch module, the target lower bridge arm switch module isthe fourth switch module and/or the fifth switch module.

The battery management module P6 may be further configured to send asecond driving signal to the main positive switch K1 in response to thethird control signal to drive the main positive switch K1 to beperiodically turned on and off, so as to enable the battery pack P1 toreceive the energy transmitted from the power supply P41, or enable thebattery pack P1 to receive the energy transmitted from the motor P3, orenable the battery pack P1 to transmit the energy to the motor P3.

In some embodiments, the battery management module P6 may send thelow-temperature-low-power heating request instruction to the controlmodule for auxiliary charging branch P8. The vehicle control unit P5 maytransmit the third control signal to the battery management module P6.

It should be noted that the voltage of the power supply P41 may behigher than the current voltage of the battery pack P1. The controlmodule for auxiliary charging branch P8 may send the first controlsignal to the auxiliary switch module in response to thelow-temperature-low-power heating request. The auxiliary switch modulemay be turned on in response to the first control signal.

The battery management module P6 may transmit the second driving signalto the main positive switch K1 in response to the third control signal.The main positive switch K1 may be periodically turned on and off inresponse to the second driving signal. During the period in which themain positive switch K1 is periodically turned on and off, the energy ofthe power supply P41 of the auxiliary charging branch P4 may betransmitted to the battery pack P1 through the switch K3, which isequivalent to charging the battery pack P1. It is worth mentioning thatthe transmission of energy from the power supply P41 of the auxiliarycharging branch P4 to the battery pack P1 through the switch K3 and theexternal ports G1 and G2 may be performed one or more times to completethe energy transmission, which is not limited herein. The purpose is tosupport self-heating of the battery pack P1 by the energy of the batterypack P1.

The battery management module P6 may send a signal to the control modulefor auxiliary charging branch P8 to instruct the auxiliary switch modulein the auxiliary charging branch P4 to be turned off. In response to thesignal, the control module for auxiliary charging branch P8 may send asignal to the auxiliary switch module to instruct the auxiliary switchmodule to be turned off, and then the auxiliary switch module is turnedoff. The vehicle control unit P5 may send the second control signal tothe motor control unit P7. The motor control unit P7 may transmit thefirst driving signal to a portion of the switch modules in the inverterP2 in response to the second control signal. The target upper bridge armswitch module and the target lower bridge arm switch module in theinverter P2 are periodically turned on and off in response to the firstdriving signal.

For example, the target upper bridge arm switch module is the firstswitch module, and the target lower bridge arm switch module is thefifth switch module. The first switch module and the fifth switch modulemay be periodically turned on and off in response to the first drivingsignal. Specifically, when the first power switch S1 and the fifth powerswitch S5 are turned on, the battery pack P1 is discharged. The currentdirection is: the battery pack P1→the main positive switch K1→the firstpower switch S1→the first stator inductor L1→the first resistor R1→thesecond resistor R2→the second stator inductor L2→the fifth power switchS5→the main negative switch K2→the battery pack P1. When the first powerswitch S1 and the fifth power switch S5 are turned off, the battery packP1 is charged. The current direction is: the first stator inductorL1→the first resistor R1→the second resistor R2→the second statorinductor L2→The diode VD2 of the second power switch S2→the mainpositive switch K1→the battery pack P1→the main negative switch K2→thediode VD4 of the fourth power switch S4—the first stator inductor L1.

The selection of the target upper bridge arm switch module and thetarget lower bridge arm switch module is not limited to the aboveexample. Different selection of the target upper bridge arm switchmodule and the target lower bridge arm switch module may correspond to adifferent discharge circuit and charging circuit of the battery pack P1,which is not limited herein.

It should be noted that, in some examples, the main positive switch K1is not turned on simultaneously with the target upper bridge arm switchmodule and the target lower bridge arm switch module. The energy of thebattery pack P1 may be transmitted to the motor P3 through the supportcapacitor C1 to enable the charging and discharging of the battery packP1.

In the case where the main positive switch K1 is driven by the seconddriving signal to be turned on, a portion of the switch modules (i.e.,the target upper bridge arm switch module and the target lower bridgearm switch module) may be driven by the first driving signal to beturned off. If the energy stored in the motor P3 is less than the energystored in the battery pack P1, the battery pack P1 may transmit energyto the support capacitor C1. If the energy stored in the motor P3 isgreater than the energy stored in the battery pack P1, the battery packP1 may receive the energy transmitted from the motor P3.

In the case where a portion of the switch modules (i.e., the targetupper bridge arm switch module and the target lower bridge arm switchmodule) is driven by the first driving signal driving to be turned on,the main positive switch K1 may be driven by the second driving signalto be turned off. The motor P3 may receive the energy transmitted fromthe support capacitor C1, and the energy of the support capacitor C1 maybe obtained from the battery pack P1.

The process of discharging and charging of the battery pack P1 describedabove may be repeated to achieve self-heating of the battery pack P1.

In another embodiment, the battery management module P6 may send thelow-temperature-low-power heating request instruction to the controlmodule for auxiliary charging branch P8, and the vehicle control unit P5may send the second control signal to the motor control unit P7.

The voltage of the power supply P41 may be greater than the currentvoltage of the battery pack P1. The control module for auxiliarycharging branch P8 may send the first control signal to the auxiliaryswitch module in response to the low-temperature-low-power heatingrequest instruction. The auxiliary switch module may be turned on inresponse to the first control signal.

The motor control unit P7 may transmit the first driving signal to aportion of the switch modules in the inverter P2 in response to thesecond control signal. The target upper bridge arm switch module and thetarget lower bridge arm switch module in the inverter P2 areperiodically turned on and off in response to the first driving signal.During a period in which the target upper bridge arm switch module andthe target lower bridge arm switch module in the inverter P2 are turnedon, the energy of the power supply P41 of the auxiliary charging branchP4 may be transmitted to the motor P3 through the switch K3, that is,the motor P3 is charged. It is worth mentioning that transmission ofenergy from the power supply P41 of the auxiliary charging branch P4 tothe motor P3 through the switch K3 and the external ports G1 and G2 maybe performed one or more times to complete the energy transmission,which is not limited herein. The purpose is to support self-heating ofthe battery pack P1 by the energy of the battery pack P1 and the energyof the motor P3.

The battery management module P6 may send a signal to the control modulefor auxiliary charging branch P8 to instruct the auxiliary switch modulein the auxiliary charging branch P4 to be turned off. In response to thesignal, the control module for auxiliary charging branch P8 may send asignal to the auxiliary switch module to instruct the auxiliary switchmodule to be turned off, and the auxiliary switch module may be turnedoff accordingly. The vehicle control unit P5 may transmit the thirdcontrol signal to the battery management module P6. The batterymanagement module P6 may transmit the second driving signal to the mainpositive switch K1 in response to the third control signal. The mainpositive switch K1 may be periodically turned on and off in response tothe second driving signal.

With periodical on-off of the main positive switch K1 and periodicalon-off of the target upper bridge arm switch module and the target lowerbridge arm switch module in the inverter P2, the energy of the batterypack P1 may be transmitted to the motor P3 and the energy of the motorP3 may be transmitted to the battery pack P1, via the support capacitorC1. For the mutual transmission of energy between the battery pack P1and the motor P3, reference may be made to the above embodiments, anddetails are not described herein again.

In yet another embodiment, the battery management module P6 may send thelow-temperature-low-power heating request instruction to the controlmodule for auxiliary charging branch P8. The vehicle control unit P5 maytransmit the second control signal to the motor control unit P7 andtransmit the third control signal to the battery management module P6.

The voltage of the power supply P41 may be greater than the currentvoltage of the battery pack P1. The control module for auxiliarycharging branch P8 may send the first control signal to the auxiliaryswitch module in response to the low-temperature-low-power heatingrequest instruction. The auxiliary switch module may be turned on inresponse to the first control signal.

The motor control unit P7 may transmit the first driving signal to aportion of the switch modules in the inverter P2 in response to thesecond control signal. The target upper bridge arm switch module and thetarget lower bridge arm switch module in the inverter P2 areperiodically turned on and off in response to the first driving signal.During a period where the target upper bridge arm switch module and thetarget lower bridge arm switch module in the inverter P2 are turned on,the energy of the power supply P41 of the auxiliary charging branch P4may be transmitted to the motor through the switch K3 and the externalports G1 and G2, that is, the motor P3 is charged.

The battery management module P6 may transmit the second driving signalto the main positive switch K1 in response to the third control signal.The main positive switch K1 may be periodically turned on and off inresponse to the second driving signal. During periodical on-off of themain positive switch K1, the energy of the power supply P41 of theauxiliary charging branch P4 may be transmitted to the battery pack P1through the switch K3 and the external ports G1 and G2, that is, thebattery pack P1 is charged.

It is worth mentioning that transmission of energy from the power supplyP41 of the auxiliary charging branch P4 to the battery pack P1 and themotor P3 through the switch K3 and the external ports G1 and G2 may beperformed one or more times to complete the energy transmission, whichis not limited herein. The purpose is to support self-heating of thebattery pack P1 by the energy of the battery pack P1 and the energy ofthe motor P3.

The battery management module P6 may send a signal to the control modulefor auxiliary charging branch P8 to instruct the auxiliary switch modulein the auxiliary charging branch P4 to be turned off. In response to thesignal, the control module for auxiliary charging branch P8 may send asignal to the auxiliary switch module to instruct the auxiliary switchmodule to be off, and then the auxiliary switch module is turned offaccordingly.

The target upper bridge arm switch module and the target lower bridgearm switch module in the inverter P2 may be periodically turned on andoff in response to the first driving signal. The main positive switch K1may be periodically turned on and off in response to the second drivingsignal. Via the support capacitor, the energy of the battery pack P1 maybe transmitted to the motor P3, and the motor P3 may transmit energy tothe battery pack P1. For the mutual transmission of energy between thebattery pack P1 and the motor P3, reference may be made to the aboveembodiments, and details are not described herein again.

It should be noted that the vehicle control unit P5, the control modulefor auxiliary charging branch P8, the battery management module P6, andthe motor control unit P7 may cooperate with each other to controlon-off of the auxiliary switch module, the switch modules in theinverter P2, and the main positive switch K1 for self-heating of thebattery pack P1. Self-heating of the battery pack P1 is not limited tothe above manner.

In some examples, the battery management module P6 may be furtherconfigured to transmit the acquired state parameter of the battery packP1 to the vehicle control unit P5. The state parameter of the batterypack P1 includes a SOC and a temperature.

The vehicle control unit P5 may also be used to transmit the receivedstate parameter of the battery pack P10 to the motor control unit P7.

The motor control unit P7 may be further configured to calculate a firstdesired frequency and a first desired duty cycle based on a desiredtemperature rising rate and the received state parameter of the batterypack P1, and to adjust a frequency and a duty cycle of the first drivingsignal to the first desired frequency and the first desired duty cycle.

The motor control unit P7 may obtain the temperature rising rate of thebattery pack P1 according to the temperature of the battery pack P1. Thedesired temperature rising rate is an expected temperature rising rate,which may be set according to specific operating scenarios and operatingrequirements, which is not limited herein. The heating rate of thebattery pack P1 may be adjusted by adjusting the frequency and dutycycle of the first driving signal to the first desired frequency and thefirst desired duty cycle. The process of calculating the first desiredfrequency and the first desired duty cycle may be performed in realtime, and the frequency and duty cycle of the first driving signal maybe adjusted in real time.

In some examples, the battery management module P6 may be furtherconfigured to transmit the acquired SOC of the battery pack P1 to thevehicle control unit P5.

The vehicle control unit P5 may be also used to transmit the receivedSOC of the battery pack P1 to the motor control unit P7.

The motor control unit P7 may be further configured to acquire a motorparameter, calculate a second desired frequency and a second desiredduty cycle based on the motor parameter, a desired motor parameter, andthe received SOC of the battery pack, and adjust the frequency and theduty cycle of the first driving signal to the second desired frequencyand the second desired duty cycle.

The motor parameter may include a phase current of the motor P3 or abusbar current. The busbar current may be the current flowing throughthe main positive switch K1. The phase current of the motor P3 may bethe current flowing into or out of the three-phase input terminal of themotor P3. The desired motor parameter may include the desired phasecurrent of the motor P3 or the desired busbar current. The desired motorparameter may be an expected motor parameter, which may be set accordingto specific operating scenarios and operating requirements, which is notlimited herein.

The heating rate of the battery pack P1 may be adjusted by adjusting thefrequency and the duty cycle of the first driving signal to the seconddesired frequency and the second desired duty cycle. The process ofcalculating the second desired frequency and the second desired dutycycle may be performed in real time, and the frequency and duty cycle ofthe first driving signal may be adjusted in real time.

In some examples, the battery management module P6 may be furtherconfigured to calculate a third desired frequency and a third desiredduty cycle based on the desired temperature rising rate and the acquiredstate parameter of the battery pack P1, and adjust the frequency and theduty cycle of the second driving signal to the third desired frequencyand the third desired duty cycle.

The state parameter of the battery pack P1 may include the SOC of thebattery pack and the temperature of the battery pack. The batterymanagement module P6 may obtain the temperature rising rate of thebattery pack according to the temperature of the battery pack. Thedesired temperature rising rate is the expected temperature rising rate,which may be set according to specific operating scenarios and operatingrequirements, which is not limited herein. The heating rate of thebattery pack P1 may be adjusted by adjusting the frequency and the dutycycle of the second driving signal to the third desired frequency andthe third desired duty cycle. The process of calculating the thirddesired frequency and the third desired duty cycle may be performed inreal time, and the frequency and the duty cycle of the second drivingsignal may be adjusted in real time.

In some examples, the motor control unit P7 may be also used to acquirethe motor parameter and send the motor parameter to the vehicle controlunit. The motor parameter may include the phase current of the motor orthe busbar current. For the phase current of the motor or the busbarcurrent, reference may be made to the related description in the aboveembodiments, which is not repeated herein.

The vehicle control unit P5 may be also used to transmit the receivedmotor parameter to the battery management module P6.

The battery management module P6 is further configured to calculate afourth desired frequency and a fourth desired duty cycle based on adesired motor parameter, the acquired SOC of the battery pack, and thereceived motor parameter, and adjust the frequency and the duty cycle ofthe second driving signal to the fourth desired frequency and the fourthdesired duty cycle. With control of the frequency and the duty cycle ofthe second driving signal, on-off frequency and on-off duration of themain positive switch K1 may be adjusted to adjust the effective value ofthe busbar current, so as to adjust the self-heating of the battery packheating system. For the desired motor parameter, reference may be madeto the related content in the above embodiments, and details are notdescribed herein again.

The process of calculating the fourth desired frequency and the fourthdesired duty cycle may be performed in real time, and the frequency andthe duty cycle of the second driving signal may be adjusted in realtime.

In some examples, the motor control unit P7 may be also used to acquirethe motor parameter and send the motor parameter to the vehicle controlunit P5. The motor parameter may include the phase current of the motoror the busbar current.

The vehicle control unit P5 may be also used to transmit the receivedmotor parameter to the battery management module P6.

The battery management module P6 may be further configured to obtain anestimated heating duration of the battery pack P1 based on the currenttemperature of the battery pack P1, the desired temperature of thebattery pack P1, the motor parameter, and the desired motor parameter.The desired temperature of the battery pack P1 may be set according tospecific operating scenarios and operating requirements, which is notlimited herein. For the desired motor parameter, reference may be madeto the related content in the above embodiments, and details are notdescribed herein again.

The battery management module P6 may be further configured to sendduration information including the estimated heating duration to thevehicle control unit P5. The value of the estimated heating duration isnot limited herein, and may be, for example, any value within 1 minuteto 40 minutes.

The vehicle control unit P5 may be also used to receive the durationinformation and issue a prompt message for prompting the estimatedheating duration. The prompt message may be implemented as imageinformation displayed on the onboard instrument, or may be implementedas sound information sent by the loudspeaker and the onboard instrument,which is not limited herein.

In addition to the low-temperature-low-power heating mode describedabove, the battery pack heating system may also enter a low-temperatureheating mode or a stop heating mode.

In some examples, the battery management module P6 may be furtherconfigured to send a low-temperature heating request instruction to thecontrol module for auxiliary charging branch P8, when it is determinedthat the temperature of the battery pack P1 is lower than the heatingtemperature threshold and the SOC of the battery pack P1 is higher thanor equal to the heating SOC requirement threshold. The low-temperatureheating request instruction is used to request the battery pack heatingsystem to enter the low-temperature heating mode.

When the SOC of the battery pack P1 is higher than or equal to theheating SOC requirement threshold, it is indicated that the energy ofthe battery pack P1 is sufficient to support self-heating of the batterypack P1. Therefore, the power supply P41 of the auxiliary chargingbranch P4 is not required to supply energy. The control module forauxiliary charging branch P8 may be further configured to send a fourthcontrol signal to the auxiliary charging branch P4 in response to thelow-temperature heating request instruction, to control the battery packheating system to be disconnected from the auxiliary charging branch P4.

In some examples, the battery management module P6 may be furtherconfigured to send a stop heating request instruction to the vehiclecontrol unit P5 and the control module for auxiliary charging branch P8respectively, when it is determined that the temperature of the batterypack P1 is higher than or equal to the heating temperature threshold andthe SOC of the battery pack P1 is higher than or equal to the heatingSOC requirement threshold. The stop heating request instruction is usedto request the battery pack heating system to enter the stop heatingmode.

The control module for auxiliary charging branch P8 may be furtherconfigured to send a fifth control signal to the auxiliary chargingbranch P4 in response to the stop heating request instruction, tocontrol the battery pack heating system to be disconnected from theauxiliary charging branch P4.

The vehicle control unit P5 may be further configured to transmit asixth control signal to the motor control unit P7 and a seventh controlsignal to the battery management module P6, in response to the stopheating request instruction.

The motor control unit P7 may be further configured to stop transmittingthe first driving signal to the portion of the switch modules in theinverter P2, in response to the sixth control signal. The switch modulesof inverter P2 are turned off.

The battery management module P6 may be further configured to stoptransmitting the second driving signal to the main positive switch K1,in response to the seventh control signal. The main positive switch K1are turned off.

In the process of heating the battery pack P1 by the battery packheating system, the motor control unit P7 may also monitor thetemperature of the switch modules in the inverter P2, the temperature atthe stator of the motor P3, the busbar current, the phase current of themotor P3 or other parameters, and upload the monitored parameters to thevehicle control unit P5. The vehicle control unit P5 may adjust thebattery pack heating system according to the parameters acquired throughthe monitoring.

The battery management module P6 may also monitor the temperature, theSOC, the insulation resistance and other parameters of the battery packP1, and upload the monitored parameters to the vehicle control unit P5.The vehicle control unit P5 may adjust the battery pack heating systemaccording to the parameters acquired through the monitoring.

The adjustment of the battery pack heating system may include: stoppingthe heating of the battery pack P1, or adjusting the first drivingsignal that is used to drive the switch modules so as to adjust theon-off frequency and the on-off duty cycle of the switch modules, oradjusting the second driving signal that is used to drive the mainpositive switch K1 so as to adjust the on-off frequency and the on-offduty cycle of the main positive switch K1.

Corresponding to the battery pack heating system in the aboveembodiments, the embodiments of the present application further providea control method for the battery pack heating system. FIG. 3 is a flowchart of a control method for a battery pack heating system according toan embodiment of the present application. As shown in FIG. 3 , thecontrol method for the battery pack heating system may include stepsS101 to S103.

In step S101, the battery management module acquires the state parameterof the battery pack, and send the low-temperature-low-power heatingrequest instruction to the vehicle control unit and the control modulefor auxiliary charging branch respectively when the state parameter ofthe battery pack meets the preset low-temperature-low-power condition.

In some examples, the state parameter includes a temperature and a SOC,and the predetermined low-temperature-low-power condition includes thetemperature being lower than the heating temperature threshold and theSOC being lower than the heating SOC requirement threshold. For example,the heating temperature threshold is greater than or equal to −50° C.and less than or equal to 5° C. The heating SOC requirement threshold isgreater than or equal to 5% and less than 100%.

In step S102, the control module for auxiliary charging branch sends thefirst control signal to the auxiliary charging branch in response to thelow-temperature-low-power heating request instruction to control thebattery pack heating system to be connected to the auxiliary chargingbranch, so as to enable the power supply to transmit energy to thebattery pack and/or the motor via the external port.

In step S103, the vehicle control unit sends, in response to thelow-temperature-low-power heating request instruction, the secondcontrol signal to the motor control unit to enable the motor controlunit to control on-off of the switch modules in the inverter, and thethird control signal to the battery management module to enable thebattery management module to control on-off of the main positive switchto enable transmission of energy between the battery pack and the motor,so as to heat the battery pack.

In the embodiments of the present application, the battery managementmodule may determine that the state parameter of the battery pack meetsthe preset low-temperature-low-power condition, and send thelow-temperature-low-power heating request instruction to the vehiclecontrol unit and the control module for auxiliary charging branchrespectively for the low-temperature-low-power heating mode. The batterymanagement module may control the control module for auxiliary chargingbranch, and the vehicle control unit may control the battery managementmodule and the motor control unit, then the auxiliary charging branch,the main positive switch and the switch modules in the inverter can becontrolled to enable the power supply of the auxiliary charging branchto transmit energy to the battery pack and/or the motor, so that thebattery pack and motor can have sufficient energy to support heating ofthe battery pack. The battery pack and the motor may transmit energy toeach other to form a cycle in which the battery pack is charged anddischarged, so that a current is generated in a circuit in which thebattery pack is located. The alternating current may continuously passthrough the battery pack, so that the internal resistor of the batterypack may emit heat. As a result, uniform and highly efficientself-heating of the battery pack can be realized even in the case of lowpower.

Corresponding to the battery pack heating system shown in FIG. 1 andFIG. 2 , FIG. 4 is a flow chat of a control method for a battery packheating system according to another embodiment of the presentapplication. FIG. 4 is different from FIG. 3 in that the control methodfor the battery pack heating system shown in FIG. 4 may further includesteps S104 to S107.

In step S104, the battery management module sends the third drivingsignal to the pre-charging switch to control the pre-charging switch tobe turned on for pre-charging.

The battery pack heating system may further include the pre-chargingbranch in parallel with the main positive switch, and the pre-chargingbranch may include the pre-charging switch and the pre-chargingresistor.

In step S105, the control module for auxiliary charging branch sends thefirst control signal to the auxiliary switch module in response to thelow-temperature-low-power heating request instruction to control theauxiliary switch module to be turned on.

The auxiliary charging branch may further include the auxiliary switchmodule. The voltage of the power supply may be higher than the currentvoltage of the battery pack.

In step S106, the motor control unit sends the first driving signal to aportion of the switch modules in the inverter in response to the secondcontrol signal to drive the portion of the switch modules to beperiodically turned on and off, so as to enable the motor to receive theenergy transmitted from the power supply, or enable the motor to receivethe energy transmitted from the battery pack, or enable the motor totransmit the energy to the battery pack.

In step S107, the battery management module sends the second drivingsignal to the main positive switch in response to the third controlsignal to drive the main positive switch to be periodically turned onand off, so as to enable the battery pack to receive the energytransmitted from the power supply, or enable the battery pack to receivethe energy transmitted from the motor, or enable the battery pack totransmit energy to the motor.

In some examples, the battery pack heating system may also include asupport capacitor in parallel with the inverter. In the case where thesecond driving signal drives the main positive switch to be turned on,the first driving signal drives the portion of the switch modules to beturned off, so as to enable the battery pack to transmit energy to thesupport capacitor, or enable the battery pack to receive energytransmitted from the motor. In the case where the first driving signaldrives the portion of the switch modules to be turned on, the seconddriving signal drives the main positive switch to be turned off, so asto enable the motor to receive energy transmitted from the supportcapacitor.

FIG. 5 is a flow chat of a control method for a battery pack heatingsystem according to yet another embodiment of the present application.FIG. 5 is different from FIG. 3 in that the control method for thebattery pack heating system shown in FIG. 5 further includes steps S108to S114.

In step S108, the battery management module determines that thetemperature of the battery pack is lower than the heating temperaturethreshold and the SOC of the battery pack is higher than or equal to theheating SOC requirement threshold, and sends the low-temperature heatingrequest instruction to the control module for auxiliary charging branch.

In step S109, the control module for auxiliary charging branch sends afourth control signal to the auxiliary charging branch in response tothe low-temperature heating request instruction, to control the batterypack heating system to be disconnected from the auxiliary chargingbranch.

In step S110, the battery management module determines that thetemperature of the battery pack is higher than or equal to the heatingtemperature threshold, and the SOC of the battery pack is higher than orequal to the heating SOC requirement threshold, and sends the stopheating request instruction to the vehicle control unit and the controlmodule for auxiliary charging branch respectively.

In step S111, the control module for auxiliary charging branch sends afifth control signal to the auxiliary charging branch in response to thestop heating request instruction, to control the battery pack heatingsystem to be disconnected from the auxiliary charging branch.

In step S112, the vehicle control unit sends, in response to the stopheating request instruction, a sixth control signal to the motor controlunit and a seventh control signal to the battery management module.

In step S113, the motor control unit stops transmitting the firstdriving signal to the portion of the switch modules in the inverter inresponse to the sixth control signal.

In step S114, the battery management module stops transmitting thesecond driving signal to the main positive switch in response to theseventh control signal.

In some examples, the motor control unit may adjust the first drivingsignal to adjust the on-off frequency and the on-off duration of theswitch modules of the inverter, so as to regulate the current used tocharge and discharge the battery pack for heating by the battery packheating system.

For example, the battery management module sends the acquired stateparameter of the battery pack to the vehicle control unit. The stateparameter may include the SOC and temperature. The vehicle control unitsends the received state parameter of the battery pack to the motorcontrol unit. The motor control unit calculates the first desiredfrequency and the first desired duty cycle based on the desiredtemperature rising rate and the received state parameter of the batterypack, and adjusts the frequency and the duty cycle of the first drivingsignal to the first desired frequency and the first desired duty cycle.

For another example, the battery management module sends the acquiredSOC of the battery pack to the vehicle control unit. The vehicle controlunit transmits the received SOC of the battery pack to the motor controlunit. The motor control unit acquires the motor parameter, andcalculates the second desired frequency and the second desired dutycycle based on the motor parameter, the desired motor parameter, and thereceived SOC of the battery pack, and adjust the frequency and the dutycycle of the first driving signal to the second desired frequency andthe second desired duty cycle. The motor parameter may include the phasecurrent of the motor or the busbar current.

In some examples, the battery management module may adjust the seconddriving signal to adjust the on-off frequency and on-off duration of themain positive switch, so as to regulate heating of the battery by thebattery pack heating system.

For example, the battery management module calculates the third desiredfrequency and the third desired duty cycle based on the desiredtemperature rising rate and the acquired state parameter of the batterypack, and adjusts the frequency and the duty cycle of the second drivingsignal to the third desired frequency and the third desired duty cycle.The state parameter may include the SOC and the temperature.

As another example, the motor control unit acquires the motor parameterand sends the motor parameter to the vehicle control unit. The motorparameter may include the phase current of the motor or the busbarcurrent. The vehicle control unit sends the received motor parameter tothe battery management module. The battery management module calculatesthe fourth desired frequency and the fourth desired duty cycle based onthe desired motor parameter, the acquired SOC of the battery pack, andthe received motor parameter, and adjusts the frequency and the dutycycle of the second driving signal to the fourth desired frequency andthe fourth desired duty cycle.

In some examples, the motor control unit acquires the motor parameterand sends the motor parameter to the vehicle control unit. The motorparameter may include the bus current or the phase current of the motor.The vehicle control unit sends the received motor parameter to thebattery management module. The battery management module obtains theestimated heating duration of the battery pack based on the currenttemperature of the battery pack, the desired temperature of the batterypack, the motor parameter, and the desired motor parameter. The batterymanagement module sends duration information including the estimatedheating duration to the vehicle control unit. The vehicle control unitreceives the duration information and issues a prompt message forprompting the estimated heating duration to prompt the user about theestimated heating duration.

For related description of the control method for the battery packheating system in the embodiment of the present application, referencemay be made to the related content of the battery pack heating system inthe above embodiments, and details are not described herein again.

It is to be understood that various embodiments in the specification aredescribed in a progressive manner. The same or similar parts between thevarious embodiments may be referred to each other, and each embodimentfocuses on a different part from other embodiments. For control methodembodiments, reference may be made to the description for theembodiments for the battery pack heating system. The disclosure is notlimited to the specific steps and structures described above andillustrated in the drawings. A person skilled in the art, afterunderstanding of the spirit of the present application, may make variouschanges, modifications and additions, or change the order between thesteps after understanding the spirit of the disclosure. Also, a detaileddescription of known method techniques is omitted herein for the sake ofbrevity.

Those skilled in the art should understand that the above embodimentsare exemplary rather than limitative. Different technical features indifferent embodiments may be combined to obtain beneficial effects.Other variations of the described embodiments can be understood andpracticed by those skilled in the art upon studying the drawings, thespecification and the claims herein. In the claims, the term“comprising” does not exclude other means or steps; the indefinitearticle “a” does not exclude a plurality of; the terms “first”, “second”are used to illustrate names rather than to indicate any particularorder. Any reference numerals in the claims should not be construed aslimiting the scope of protection. The functions of the various parts inthe claims may be implemented by a single hardware or software module.The presence of certain features in different dependent claims does notindicate that these technical features cannot be combined to achievebeneficial effects.

What is claimed is:
 1. A battery pack heating system, comprising: a mainpositive switch, a main negative switch, an inverter, an external port,a motor, an auxiliary charging branch, a control module for auxiliarycharging branch, a vehicle control unit, a motor control unit, and abattery management module, wherein: the main positive switch isconfigured to be connected to a positive electrode of a battery pack;the main negative switch is configured to be connected to a negativeelectrode of the battery pack; the inverter is connected to the mainpositive switch and the main negative switch and comprises a pluralityof switch modules; the external port is connected to the inverter andthe auxiliary charging branch, and the auxiliary charging branchcomprises a power supply and an auxiliary switch module; the batterymanagement module is configured to acquire a state parameter of thebattery pack, wherein the state parameter comprises a temperature and astate of charge, SOC, of the battery pack, and send, when thetemperature is lower than a heating temperature threshold and the SOC islower than a heating SOC requirement threshold, alow-temperature-low-power heating request instruction to the vehiclecontrol unit and the control module for auxiliary charging branchrespectively; the control module for auxiliary charging branch isconfigured to send a first control signal to the auxiliary chargingbranch in response to the low-temperature-low-power heating requestinstruction, wherein the auxiliary switch module in the auxiliarycharging branch is turned on in response to the first control signal;and the battery management module is further configured to send, inresponse to a third control signal, a second driving signal to the mainpositive switch to drive the main positive switch to be periodicallyturned on or off, wherein the third control signal is sent from thevehicle control unit to the battery management module in response to thelow-temperature-low-power heating request instruction, and whereinduring the main positive switch is periodically turned on or off, thebattery pack is charged by energy of the power supply of the auxiliarycharging branch; the battery management module is further configured tosend a signal to the control module for auxiliary charging branch toinstruct the auxiliary switch module in the auxiliary charging branch tobe turned off; the control module for auxiliary charging branch isfurther configured to send, in response to the signal, a signal to theauxiliary switch module to instruct the auxiliary switch module to beturned off, and then the auxiliary switch module is turned off; thevehicle control unit is configured to send, in response to thelow-temperature-low-power heating request instruction, a second controlsignal to the motor control unit to enable the motor control unit tocontrol the switch modules in the inverter to be periodically turned onor off to enable transmission of energy between the battery pack and themotor, so as to heat the battery pack.
 2. The battery pack heatingsystem of claim 1, wherein: the motor control unit is further configuredto send, in response to the second control signal, a first drivingsignal to a portion of the switch modules in the inverter to drive theportion of switch modules to be periodically turned on and off.
 3. Thebattery pack heating system of claim 2, wherein the inverter comprises afirst phase bridge arm, a second phase bridge arm, and a third phasebridge arm connected in parallel, the first phase bridge arm, the secondphase bridge arm, and the third phase bridge arm each comprise an upperbridge arm and a lower bridge arm, and the upper bridge arm is providedwith a switch module, and the lower bridge arm is provided with a switchmodule; wherein: the switch modules that are turned on in response tothe first driving signal comprise a target upper bridge arm switchmodule and a target lower bridge arm switch module, the target upperbridge arm switch module is the switch module of the upper bridge arm ofany bridge arm of the first phase bridge arm, the second phase bridgearm, and the third phase bridge arm, and the target lower bridge armswitch module is the switch module of the lower bridge arm of at leastone of the first phase bridge arm, the second phase bridge arm, and thethird phase bridge arm other than the bridge arm that comprises thetarget upper bridge arm switch module; the switch module comprises adiode; for the switch module of the upper bridge arm, an anode of thediode is connected to a connection point of the upper bridge arm and thelower bridge arm, and a cathode of the diode is located between theupper bridge arm and the main positive switch; for the switch module ofthe lower bridge arm, an anode of the diode is located between the lowerbridge arm and the main negative switch, and a cathode of the diode isconnected to connection point of the upper bridge arm and the lowerbridge arm; a first phase input terminal, a second phase input terminal,and a third phase input terminal of the motor are respectively connectedto a connection point of the upper bridge arm and the lower bridge armof the first phase bridge arm, a connection point of the upper bridgearm and the lower bridge arm of the second phase bridge arm, and aconnection point of the upper bridge arm and the lower bridge arm of thethird phase bridge arm.
 4. The battery pack heating system of claim 1,wherein the battery pack heating system further comprises a supportcapacitor connected in parallel with the inverter, wherein: in a casewhere the second driving signal drives the main positive switch to beturned on, the first driving signal drives the portion of the switchmodules to be turned off, so as to enable the battery pack to transmitenergy to the support capacitor, or enable the battery pack to receiveenergy transmitted from the motor; and in a case where the first drivingsignal drives the portion of the switch modules to be turned on, thesecond driving signal drives the main positive switch to be turned off,so as to enable the motor to receive energy transmitted from the supportcapacitor.
 5. The battery pack heating system of claim 1, wherein: themotor control unit is further configured to acquire a motor parameter,and send the motor parameter to the vehicle control unit, wherein themotor parameter comprises a phase current of the motor or a busbarcurrent; the vehicle control unit is further configured to send thereceived motor parameter to the battery management module; and thebattery management module is further configured to obtain an estimatedheating duration of the battery pack based on a current temperature ofthe battery pack, a desired temperature of the battery pack, the motorparameter, and a desired motor parameter, and send duration informationincluding the estimated heating duration to the vehicle control unit;and the vehicle control unit is further configured to receive theduration information, and issue a prompt message for promoting theestimated heating duration.
 6. A control method for the battery packheating system of claim 1, comprising: acquiring, by the batterymanagement module, a state parameter of the battery pack, wherein thestate parameter comprises a temperature and a state of charge, SOC, ofthe battery pack, and sending a low-temperature-low-power heatingrequest instruction to the vehicle control unit and the control modulefor auxiliary charging branch respectively when the temperature is lowerthan a heating temperature threshold and the SOC is lower than a heatingSOC requirement threshold; sending, by the control module for auxiliarycharging branch, a first control signal to the auxiliary charging branchin response to the low-temperature-low-power heating request instructionwherein the auxiliary switch module in the auxiliary charging branch isturned on in response to the first control signal; sending, by thebattery management module in response to a third control signal, asecond driving signal to the main positive switch to drive the mainpositive switch to be periodically turned on or off, wherein the thirdcontrol signal is sent from the vehicle control unit to the batterymanagement module in response to the low-temperature-low-power heatingrequest instruction, and wherein during the main positive switch isperiodically turned on or off, the battery pack is charged by energy ofthe power supply of the auxiliary charging branch; sending, by thebattery management module, a signal to the control module for auxiliarycharging branch to instruct the auxiliary switch module in the auxiliarycharging branch to be turned off; sending, by the control module forauxiliary charging branch in response to the signal, a signal to theauxiliary switch module to instruct the auxiliary switch module to beturned off, and then the auxiliary switch module is tuned off; andsending, by the vehicle control unit in response to thelow-temperature-low-power heating request instruction, a second controlsignal to the motor control unit to enable the motor control unit tocontrol the switch modules in the inverter to be periodically turned onor turned off to enable transmission of energy between the battery packand the motor, so as to heat the battery pack.
 7. The control method forthe battery pack heating system of claim 6, further comprising: sending,by the motor control unit in response to the second control signal, afirst driving signal to a portion of the switch modules in the inverterto drive the portion of switch modules to be periodically turned on andoff.
 8. The control method for the battery pack heating system of claim6, wherein the battery pack heating system further comprises a supportcapacitor connected in parallel with the inverter, wherein: in a casewhere the second driving signal drives the main positive switch to beturned on, the first driving signal drives the portion of the switchmodules to be turned off, so as to enable the battery pack to transmitenergy to the support capacitor, or enable the battery pack to receiveenergy transmitted from the motor; and in a case where the first drivingsignal drives the portion of the switch modules to be turned on, thesecond driving signal drives the main positive switch to be turned off,so as to enable the motor to receive energy transmitted from the supportcapacitor.
 9. The control method for the battery pack heating system ofclaim 6, further comprising: acquiring, by the motor control unit, amotor parameter, and sending the motor parameter to the vehicle controlunit, wherein the motor parameter comprises a phase current of the motorof a busbar current; sending, by the vehicle control unit, the receivedmotor parameter to the battery management module; obtaining, by thebattery management module, an estimated heating duration of the batterypack based on a current temperature of the battery pack, a desiredtemperature of the battery pack, the motor parameter, and a desiredmotor parameter; sending, by the battery management module, durationinformation including the estimated heating duration to the vehiclecontrol unit; and receiving, by the vehicle control unit, the durationinformation, and issuing a prompt message for prompting the estimatedheating duration.